A conventional pressure switch 9 is shown in FIG. 9 and generally includes a push member 91, a first plate 92, a second plate 93, a first contact point 94, a second contact point 95, a spring member 96 and a rectangular box 97 which receives all the parts therein. When the pressure of water is too low, the pump can be automatically activated to maintain a desired pressure in pipes.
When the pressure of water is high, the push member 91 pushes the first plate 92 which drives the second plate 93 and the first contact point 94 is moved by the second plate 93 to be separated from the second contact point 95 so as to stop the pump.
When the water pressure in pipes is lowered and smaller than the spring force of the spring member 96 in the pressure switch 9, the spring member 96 drives the two contact points 94, 95 to be in contact with each other to activate the pump.
However, when the direction of water flow form the inlet 98 and the swing direction of the first contact point 94 need a certain space to work so that the box 97 has to be large enough to receive all the parts therein. Besides, the inlet 98 is located off from the center of the box 97 so that it requires a larger space to install the box 97.
The present invention intends to provide a pressure switch wherein the direction of water flow form the inlet and the swing direction of the contact point are the same so that the box can be a cylindrical box and the inlet is located at the central axis of the box. This reduces the manufacturing cost.